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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y40/00—Manufacture or treatment of nanostructures
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  • C01B32/00—Carbon; Compounds thereof
  • C01B32/15—Nano-sized carbon materials
  • C01B32/158—Carbon nanotubes
  • C01B32/168—After-treatment
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/20—Light-sensitive devices
  • H01G9/2027—Light-sensitive devices comprising an oxide semiconductor electrode
  • H01G9/2031—Light-sensitive devices comprising an oxide semiconductor electrode comprising titanium oxide, e.g. TiO2
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
  • H10K85/20—Carbon compounds, e.g. carbon nanotubes or fullerenes
  • H10K85/221—Carbon nanotubes
  • H10K85/225—Carbon nanotubes comprising substituents
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  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2002/00—Crystal-structural characteristics
  • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
  • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/03—Particle morphology depicted by an image obtained by SEM
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/01—Particle morphology depicted by an image
  • C01P2004/04—Particle morphology depicted by an image obtained by TEM, STEM, STM or AFM
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/20—Light-sensitive devices
  • H01G9/2059—Light-sensitive devices comprising an organic dye as the active light absorbing material, e.g. adsorbed on an electrode or dissolved in solution
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/542—Dye sensitized solar cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E10/00—Energy generation through renewable energy sources
  • Y02E10/50—Photovoltaic [PV] energy
  • Y02E10/549—Organic PV cells

Definitions

• the invention relates to high efficient dye-sensitized solar cells using TiO 2 -carbon nano tube (MWCNT) nanocomposite.
• MWCNT TiO 2 -carbon nano tube
• the invention relates to TiO 2 -MWCNT nanocomposites prepared by hydrothermal route which result in higher efficiency of the dye sensitized solar cell.
• the solar cell performance in dye sensitized or hybrid solar cells is adversely affected by the low efficiency of transfer of photo-generated charges to the electrodes.
• CNT can provide direct and efficient path for such photo generated electrons, hence composites of CNT with metal oxides have been proposed.
• Sol-gel and electrophoresis methods to synthesize TiO 2 - MWCNT nanocomposites have been attempted, but the physical and electronic attachment between TiO 2 nanoparticles and the CNT does not seem to be strong enough in these cases, such that it can prevent recombination of the photo-generated charges strongly.
• Nanorods/Nanoparticles TiO 2 for Photocatalytic Activity and Dyesensitized Solar Cell Applications
• Sorapong Pavasupree et.al. published in Materials Research Society discloses Nanorods/nanoparticles TiO 2 with mesoporous structure synthesized by hydrothermal method at 150 0 C for 20 h.
• the solar energy conversion efficiency of the cell using nanorods/nanoparticles TiO 2 with mesoporous structure was about 7.12 %.
• Page 5131 discloses fabrication of dye sensitized solar cell using TiO 2 coated multiwalled carbon nanotubes (MWCNT) by sol-gel method with 0.1 wt% of MWCNT and thickness of 10-15 microns with efficiency of 4.97%.
• MWCNT TiO 2 coated multiwalled carbon nanotubes
• present invention provides a hydrothermal process for the preparation of Titanium dioxide-Multi-walled carbon nanotubes (TiO 2 -MWCNT) nanocomposite, and the said process comprising the steps of: i. hydrolyzing Titanium compound precursor in water; ii. sonicating hydrolysed presoursor of step (a) with MWCNTs; iii. transferring product of step (b) to autoclave vessel with H 2 S ⁇ 4 and kept at 150-200 0 C for 12-24 hours; iv. washing product of step (c) with water; and v. drying the product of step (d) at about 50-60 0 C in dust proof environment to obtain TiO 2 -CNT nanocomposite.
• the present invention provides titanium precursor/compound which is hydrolysable at room temperature, preferably 20-30 0 C, preferably titanium isopropoxide or titanuim chloride.
• the present invention provides Titanium dioxide-Multi-walled carbon nanotubes (TiO 2 -MWCNT) nanocomposite prepared by the hydrothermal process wherein the wt % of CNT with respect to TiO 2 in the nanocomposite used is in the range of 0.01 -0.5 wt %.
• the present invention provides titanium dioxide-Multi- walled carbon nanotubes (TiO 2 -MWCNT) nanocomposite prepared by the hydrothe ⁇ nal process, wherein the thickness of said nanocomposite film is 1-15 microns.
• the present invention provides a process for the preparation of a solar cell using Titanium dioxide-Multi-walled carbon nanotubes (TiO 2 -MWCNT) nanocomposite, wherein the said process comprising the steps of:
• step (v) of claim 1 putting 200 microlitre drops of the TiO 2 -CNT nanocomposite as obtained in step (v) of claim 1 on Flourine doped tin oxide conductive and hydrolyzed glass substrate; II. controlling the thickness of the film with 0.5 micron-thick scotch tape; forming film by doctor-blading process; HI. heat treating the film as obtained in step (h) at a temperature of 450°C for 1 h.
• step (i) sensitizing TiO 2 -CNT nanocomposite film as obtained in step (i) with standard ruthenium-based N3-dye to obtain dye sensitized TiO 2 -CNT nanocomposite film;
• step (j) preparing electrode by using dye sensitized TiO 2 -CNT nanocomposite film as obtained in step (j);
• step (k) prepareing dye sensitized TiO 2 -CNT nanocomposite solar cell by using electrode as obtained in step (k), counter electrode and liquid electrolyte.
• counter electrode used is platinum- coated FTO (Pt-FTO) substrate.
• liquid electrolyte consisting of 0.1 M lithium iodide, 0.05M iodine in acetonitrile.
• the improved efficiency of solar cell ranges between 5- 15%.
• efficiency of solar cell is greater than 5 %.
• Figure 1 Transmission Electron Microscopy (TEM), Field-Emission Scanning Electron Microscope (FE-SEM, Hitachi S-4200) images of Titanium di-oxide and MWCNTs nano composites of the invention prepared by the hydrothermal process.
• Figure Ia shows the Transmission Electron Microscopy (TEM) image of TiO 2 nanoparticles synthesized by the hydrothermal process without incorporation of MWCNT. The mean particle size is about 8- 10 nm and the particles are faceted suggesting good crystallinity in the hydrothermal process.
• Figure Ib shows TEM image of MWCNTs used in the experiment indicating its dimensions (Diameter ⁇ 20-40nm and length -5-15 ⁇ m). The integration between MWCNT and TiO 2 is seen from the Field-Emission Scanning Electron Microscope (FE-SEM) data shown in Fig. Ic. A uniform growth with excellent TiO 2 NPs coverage can be clearly seen.
• TEM Transmission Electron Microscopy
• FE-SEM Field-Emission Scanning
• Figure 2 FT-IR spectrum of Titanium di-oxide and MWCNTs nano composites of the invention prepared by the hydrothermal process.
• Figure 2a shows the FTIR data of (a) pristine MWCNTs, (b) TiO 2 nanoparticles, (c) hydrothermally processed MWCNTs and (d) TiO 2 -MWCNTs nanocomposites.
• the bonding between Ti-O is clearly represented in the region near 500 cm '1 . It is interesting to note from the black and red arrows in this region that the mean position of the signature shifts from about 520 cm '1 in the TiO 2 case to about 612 cm '1 for the TiO 2 -MWCNT composite.
• present invention provides a composition comprising nanocomposites of Titanium dioxide and carbon nanotubes (CNT) prepared by hydrothermal process.
• the TiO 2 - CNT nanocomposites of the invention are prepared by the hydrothermal route.
• the TiO 2 - CNT nanocomposites of the invention prepared by the hydrothermal route are used for improvement of efficiency of solar cells to greater than 5 %.
• the hydrothermal process of preparation of the composition of the invention comprises a Ti compound/precursor.
• the Ti compound/precursor preferably are titanium isopropoxide or titanuim chloride and such which are hydrolysable at room temperature, particularly 20- 30 0 C.
• the CNT of the invention are preferably multi-walled.
• the TiO 2 -CNT nanocomposites of the invention are prepared by the hydrothermal process comprising:
• step (b) sonicating presoursor of step (a) with CNTs; (c) transferring procduct of step (b) to autoclave vessel with H 2 SO 4 and kept at 150-200 0 C for 12-24 hours; (d) washing product of step (c)with water, and
• step (e) drying the product of step (d)at about 50-60 deg C in dust proof environment.
• the wt % of CNT with respect to TiO 2 is in the range of 0.01-0.5wt %.
• Sulphuric acid is added in the range of 2-5 ml
• the autoclave vessel is preferably Teflon coated and the process is carried out at 150-200 deg C for 12-24 hours. The product hence obtained is dried at 50-60 deg C.
• the CNTs of the invention are optionally modified by chemical processes selected from acid treatment, base treatment, organic, organometallic attachment and such like and physical processing selected from mechanical, thermal, plasma, radiation treatment and such like.
• the TiO 2 -CNT nanocomposites of the invention are characterized by Transmission Electron Microscope (TEM), Field-Emission Scanning Electron Microscope (FE-SEM) and FT-IR spectroscopy.
• TEM Transmission Electron Microscope
• FE-SEM Field-Emission Scanning Electron Microscope
• FT-IR spectroscopy The FTIR data suggest that the -COOH groups open up on the surface of MWCNT under hydrothermal processing conditions and these conjugate with the Ti precursor to yield a composite. This integral conjugation is effective in the charge transfer process.
• This efficient charge transfer from TiO 2 to MWCNT and the efficient electron transport by the latter improves the efficiency of the solar cell by greater than 5 %, thus achieving the objective of the invention of improving performance of solar cells.
• the nanocomposite of the invention prepared by the hydrothermal process improve the efficiency of the solar cells to greater than 5% as exemplified herein.
• the TiO 2 -CNT nanocomposites prepared by sol-gel method gave maximum solar cell efficiency of 4.97% and Pavasupree et al wherein nanorods and nanoparticles of TiO 2 with mesoporous structures gave an efficiency of 7.12%
• the TiO 2 -CNT nanocomposites prepared by hydrothermal process of the invention gave improved solar cell efficiency in the range of 5-15%.
• the thickness of the nanocomposite of the invention in the solar cell as exemplified herein is in the range of 1-20 microns and shows efficiency in the range of 5- 15 %.
• the TiO 2 -MWCNTs nanocomposite was prepared by using hydrothermal method. Titanium Isopropoxide (2 ml) was hydrolyzed by adding sufficient amount of deionized water and then 5 milligrams of MWCNTs were added to the above solution followed by sonication for 5 minutes. The solution was then transferred to Teflon lined autoclave vessel along with 3ml Of H 2 SO 4 (IM). This autoclave vessel was kept at 175 0 C for 24 hours. The resulting product was washed thoroughly with deionized water and dried at 50 0 C in a dust proof environment to produce grayish powder OfTiO 2 -MWCNTs nano composite.
• IM Teflon lined autoclave vessel along with 3ml Of H 2 SO 4
• Example 2 Preparation OfTiO 2 -CNT nanocomposite dye sensitized solar cell
• the conductive glass substrates were first hydrolyzed in boiling distilled water for 30 min and air-dried. Parallel edges of each substrate were covered with 0.5 micron-thick scotch tape to control the thickness of the film.
• a few drops of the resultant TiO 2 -CNT nanocomposite were then placed onto the (FTO) Flourine doped tin oxide substrates and the films were formed by doctor-blading process. The films were then immediately heat-treated at a temperature of 450°C for 1 h.
• the TiO 2 -CNT nanocomposite films were sensitized with standard ruthenium-based N3-dye. The films were immersed in N3-dye with a concentration of 0.3mM in ethanol for 24 hours. The samples were then rinsed with ethanol to remove excess dye on the surface and air-dried at room temperature. A spacer was placed at each edge of the TiO 2 -CNT nanocomposite film electrode and the counter electrode consisting of a platinum- coated FTO (Pt-FTO) substrate was placed on top, with the Pt- coated side of each FTO substrate facing the TiO 2 -CNT nanocomposite film electrode. The two electrodes were then sandwiched together with two metal clips.
• Pt-FTO platinum- coated FTO
• liquid electrolyte consisting of 0.1 M lithium iodide, 0.05M iodine in acetonitrile.
• drops of the liquid electrolyte were introduced to one edge of the sandwich, so that the liquid electrolyte spread in between the two electrodes.
• the light source was placed next to each solar cell device, allowing light to penetrate through the FTO back contact to the TiO 2 -CNT nanocomposite film electrode with a constant light source intensity of - 100 mW/cm 2 .
• the resulting current-voltage curves of the cells in the dark and as a function of incident light intensity were used to derive the open-circuit voltage (Voc) and the short-circuit current density (Jsc).
• Voc open-circuit voltage
• Jsc short-circuit current density
• a spot size of 0.28 cm 2 was used in all measurements and was taken as the active area of each solar cell sample.
• the I-V characteristics as a function of incident light intensity was used to obtain the open- circuit voltage (Voc), short-circuit current density (Jsc).
• the values found from the I-V curves were then used to derive values for the fill factor (FF), the overall power conversion efficiency ( ⁇ ) for each solar cell.
• FF fill factor
• ⁇ overall power conversion efficiency
• the solar cell as fabricated with the nanocomposite as described in example 2 with thickness of about 2 ⁇ m (micrometer) with 0.12wt% of multi walled carbon nanotubes showed an efficiency of 5.6%
• the solar cell as fabricated with the nanocomposite as described in example 2 with thickness of about 2 ⁇ m (micrometer) with 0.25wt% of multi walled carbon nanotubes showed an efficiency of 5.16%
• the solar cell as fabricated with the nanocomposite as described in example 2 with thickness of 10-12 ⁇ m (micrometer) with 0.12 wt% of multi walled carbon nanotubes showed an efficiency of 7.60%.
• the solar cell as fabricated with the nanocomposites as described in example 2 with thickness of 10-12 ⁇ m (micrometer) with 0.25 wt% of multi walled carbon nanotubes showed an efficiency of 7.37% ADVANTAGES OFTHE INVENTION
• the main advantage of the present invention is the use of hydrothermally synthesized ⁇ 02-CNT nanocomposite in solar cell.
• Another advantage of the invention is the interrelation of the thickness of the oxide layer as well as content of the CNT and its optimization to achieve the maximum conversion efficiency upto 7.6 %.

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• 2010
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